extern void write_char(char ch);

void check_a20_valid() {
  unsigned char *p0 = 0x0;
  unsigned char *p1 = 0x100000;
  for (unsigned char i = 0; i < 10; ++i) {
    *p0 = i;
    if (*p0 != *p1) {
      write_char('b');
      break;
    } else {
      write_char('e');
    }
  }
}

void lan_main() {
  write_char('L');
  write_char('O');
  write_char('V');
  write_char('E');
  check_a20_valid();
  while (1)
    ;
}
